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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 168 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.353 − 99 =
  2. 2.375 + 99 =
  3. 3.388 + 99 =
  4. 4.29 + 19 =
  5. 5.197 + 99 =
  6. 6.763 − 99 =
  7. 7.35 + 9 =
  8. 8.45 − 29 =
  9. 9.535 − 99 =
  10. 10.29 + 9 =
  11. 11.38 − 29 =
  12. 12.708 − 99 =
  13. 13.83 − 9 =
  14. 14.67 + 29 =
  15. 15.34 − 19 =
  16. 16.27 − 9 =
  17. 17.95 − 19 =
  18. 18.42 + 29 =
  19. 19.41 − 19 =
  20. 20.28 + 9 =
  21. 21.20 − 9 =
  22. 22.42 + 19 =
  23. 23.62 + 29 =
  24. 24.75 − 29 =
  25. 25.70 − 29 =
  26. 26.79 + 29 =
  27. 27.479 + 99 =
  28. 28.15 + 29 =
  29. 29.106 − 29 =
  30. 30.50 − 29 =
  31. 31.606 − 99 =
  32. 32.78 − 29 =
  33. 33.22 − 19 =
  34. 34.27 − 19 =
  35. 35.32 + 29 =
  36. 36.26 + 9 =
  37. 37.75 + 19 =
  38. 38.159 + 99 =
  39. 39.31 − 19 =
  40. 40.34 − 9 =

Answer key

  1. 254
  2. 474
  3. 487
  4. 48
  5. 296
  6. 664
  7. 44
  8. 16
  9. 436
  10. 38
  11. 9
  12. 609
  13. 74
  14. 96
  15. 15
  16. 18
  17. 76
  18. 71
  19. 22
  20. 37
  21. 11
  22. 61
  23. 91
  24. 46
  25. 41
  26. 108
  27. 578
  28. 44
  29. 77
  30. 21
  31. 507
  32. 49
  33. 3
  34. 8
  35. 61
  36. 35
  37. 94
  38. 258
  39. 12
  40. 25

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